Camera-based evaluation of bird collisions with wind turbines
As part of the energy system change, the German government is aiming to drastically accelerate the expansion of renewable energies (BMU 2010, 2004). Along with the USA, Germany plays a leading role in the wind energy sector (Hötker et al. 2013). Especially in southern Germany, renewable electricity generation cannot meet the current and forecast demand.
The reasons for this lie in numerous obstacles in the project planning of wind power plants. A major problem arises from the European protection of species, especially the prohibition of killing according to § 44 BNatSchG (German Federal Nature Conservation Act). Among other things, certain raptor species are particularly sensitive to wind turbines (Grünkorn et al. 2016, Hötker et al. 2013, Miosga et al. 2013). This is also shown by the evaluations of the Federal German Impact Victim Index, which was able to assign 37% of all findings to birds of prey (Dürr 2013 in Hötker et al. 2013). This includes numerous protected species (e.g. Annex I, EC Birds Directive) such as the Red Kite (Milvus milvus) which, due to its predominantly endemic occurrence in Europe and 50% of the breeding population (Mebs & Schmidt in Walz 2005) in the Federal Republic of Germany, requires particularly responsible management.
The exact circumstances of the numerous collisions are not yet comprehensively known (e.g. May et al. 2015). Therefore, minimum distances to eyrie sites (e.g. LAG VSW 2015), deflection areas as well as measures for temporal shutdown are used in the selection of suitable wind power sites and the subsequent approval in order to reduce the risk of collision (see e.g. LUBW 2013). Since the assessment of the "significantly increased risk of killing" is difficult to predict, no permission has been granted for a large number of planned installations in recent years, also for reasons of species protection.
Technical avoidance measures, such as automatic shutdown by pulses or the emission of acoustic warning or scaring signals triggered by monitoring devices (cameras, radars) and thus intended to prevent collisions, have so far only been investigated to a limited extent in terms of their effectiveness. Studies have been carried out in Switzerland (Aschwanden et al. 2015) and Norway (May et al. 2012), among others, but due to small samples and special natural conditions, the transferability of statements on effectiveness to Germany is limited. Therefore, these technical avoidance measures are not accepted by the authorities in Germany, as their effect has not yet been clearly proven.
In order to fill this knowledge gap with technically sound data, there is a need for a systematic determination of the effectiveness of technical avoidance measures. Tests of collision avoidance systems have so far concentrated on areas outside Bavaria and on turbine sites outside forests (Bruns et al. 2020). In the future, however, the expansion of wind energy will also be necessary for forests and will require an adapted species conservation assessment (Richarz 2014).
Objectives
To ensure that the framework conditions for the formulation of effective avoidance and mitigation measures in the context of an immission control procedure can succeed, the following contents must be investigated in the course of the project:
1. Principles and guard rails of needs-based shutdown - evaluation of risk management measures
The priority of the project is to evaluate what camera-based collision avoidance systems must achieve in order to be recognised as effective collision avoidance systems. The research content is structured according to the relevant performance characteristics of the camera systems involved (KNE 2019; Bruns et al. 2021).
This includes the spatial and temporal coverage of the systems, their detection range as well as the detection accuracy of bird species at risk of collision, in particular red kite and black kite. For this purpose, the data from the camera systems is compared with reference data obtained through ornithological plan observations.
2. Effectiveness and efficiency of system response
To assess the performance of a technical collision avoidance system, the effectiveness (shutdown of WTs) and efficiency (number and duration of shutdowns in relation to required and non-required shutdowns) are quantitatively evaluated.
In this context, it is investigated how often and under which circumstances (e.g. rotor speed, weather, bird behaviour) dangerous flights occur in the area of the WT and how often correct or erroneous shutdown signals are sent.
Camera systems can be used for preliminary investigations in the context of immission control procedures. This has the significant advantage that the data can be directly linked to the monitoring data of the camera systems installed on the turbines. As a result, it is much easier to assess the collision risk for individuals of certain species before granting a permit. This is intended to help estimate the inevitably higher number of observations by camera systems compared to plan sightings, and also to evaluate significance levels concerning the risk of collision.
For this purpose, the basic activity patterns of the target species are investigated as a function of daytime, season and weather. As the planned wind turbines will be built and taken into operation in the second year of the project, it is possible to compare the number and circumstances of potential collision events with the occurrence of the species before the wind turbines were commissioned. Likewise, by opposing the flights before and after the commissioning of the WTs, it is possible to investigate whether avoidance behaviour occurs in the target species.
Framework conditions of the trial
In order to clarify the research questions of the project, an area with a high breeding occurrence of the target species Red Kite and Black Kite was selected. Camera-based collision avoidance systems have so far only been tested at open land sites, while there are still no comparative values for forested sites. These conditions will be fulfilled by the Fuchstal turbine site.
In the area of the planned wind turbines, two camera systems from the manufacturer Identiflight will be tried out, starting in the summer of 2022. These are installed on towers at a height of 40m to enable an overview of the forest site.
Trained observers will be used for the comparative studies. Flying objects are classified and identified through ornithological observations. The observation is limited to random samples and takes place in regular intervals over a period of 4 growing seasons (2022-2025).
